The invention relates to a method for regulating the brake(s) of an escalator or a moving walkway.
For stopping the step or pallet band of an escalator or a moving walkway in response to safety elements, mechanically or electromechanically actuated brakes, in particular shoe brakes, have essentially been used so far. These brakes are usually spring-loaded, the effect of the spring being eliminated by a magnet coil, such that the brake remains opened in the operating state. When stopping the escalator or moving walkway the effect of the electromagnet is eliminated and thereby the thus prevailing spring force is made use of. Usually the braking area and the balance weight are located independently from each other, but normally they form a coherent system in form of a brake drum. The balance weight serves for maintaining the brake path within the predetermined limits. An essential criterion for dimensioning the balance weight is the load caused by the number of passengers and for moving walkways it is essentially the length in connection with the passenger load thereon.
In case the emergency stopping device is actuated or safety switches and other safety means respond, the driving unit will be separated from the power supply. Simultaneously the brake will be applied.
The disadvantage of the known brake is that the brake is in part applied in a load dependent manner, that no equal brake paths can be obtainedxe2x80x94since they are dependent on the loadxe2x80x94, and that under certain constructional conditions (for instance excessive length of moving walkways) such big balance weights are required, that one reaches technical limits regarding the accommodation. Furthermore, a higher wear of the brake linings can be expected, whereby a continuous adjustment of the mechanical brakes becomes necessary due to safety reasons.
From DE-A-35 09 207, a method and an apparatus for stopping sliding passenger transport installations, for instance an escalator, are known, in which the movement of the escalator is stopped in a controlled way, essentially independently from the load and the moving direction of the escalator. The deceleration is monitored and controlled continuously by a signal, which is provided by a speed converter, for instance a speedometer generator. Direct current is supplied to the windings of an alternating current motor serving as drive motor, the electrodynamic braking effect generated in the motor causing predetermined deceleration behaviour of the movement of the escalator. In the braking case, the windings of the drive motor are preferably supplied with a pulsating d.c. voltage, which is formed and controlled by means of a thyristor circuit, which is controlled by electronic elements, and which provides a reference speed value for the escalator on the base of the speed of the escalator provided by a speed converter, for instance a speedometer.
Recently, frequency converters have been used for braking passenger transport installations, in particular escalators and moving walkways, so that, in certain circumstances, mechanical brakes as operational brakes to a large extent are no longer required. However, the frequency converters represent elements, which cause higher costs and may thus not be desired by clients in certain circumstances.
The U.S. Pat. No. 4,664,247 describes a brake control device for passenger conveyors such as escalators and moving walkways. The device relates to a sensor for measuring the speed of the passenger conveyor system (actual value) and generates an actual speed signal in analog form. A control signal that is also analog is furthermore generated (desired value). A comparison of the analog desired value and the actual value occurs in a following control device. The automatic controller generates a control signal that acts upon the braking magnet of a braking system in a delayed manner, such that a soft, step-by-step delay is possible, wherein the actual value must remain near the desired value. This device is designed to activate the brake gradually, meaning in a quasi analog form. An additional high-frequency signal is provided as control criterion for the brake, which varies step-by-step within a predetermined time interval between 100% and 0%, as well occurs. As a result of fluctuations in this high-frequency signal, in the detailed form, the actual load applies to the passenger conveyor (number of persons) is not actually taken into account, so that during a gradual braking of the passenger conveyor the braking is not considered to be uncomfortable by the users.
It is the object of the invention to improve a method for regulating the brake(s) of an escalator or a moving walkway, such that a control schema is formed, which, independent of the respectively applied load on the escalator or the moving walkway, can if necessary be integrated into existing systems without requiring particular assembly and cost expenditure.
This object is achieved by the method of the present invention, which utilizes one or more nominal stored speed values and compares them with actual speed values to provide control of the braking process in an escalator or moving walkway.
Other advantageous embodiments of the invention include use of sensors to provide actual speed values for comparison, use of fuzzy logic in carrying out brake control, and actuating a brake magnet independent of an energy supply for a drive of an escalator or moving walkway.
A braking device operating according to the method of the invention comprises at least one, in particular spring-loaded brake, e.g., a shoe brake, which can be controlled by at least one brake magnet, which deviating from this state of the technology can be controlled by a regulator performing a discontinuous actual value/desired value comparison.
Thus, the object of the invention provides a preferably closed control circuit, which can also be retrofitted in existing installations, and which can be integrated into new installations, on the one hand, and existing installations, on the other hand, without great expenditure and assembly.
The method according to the invention thus permits a load-independent braking of the step or pallet band for escalators and moving walkways, as compared to the known prior art, which essentially has the following advantages:
always equal brake paths, since independent from the load;
low wear of the operational brake, in particular of the brake shoes of a show brake;
at least partial reduction of the balance weight;
at least partially smaller dimensioning of the drive motor.
Using the method according to the invention respectively the braking device operating according to it, the speed of the escalator or moving walkway can be decreased in a defined way to the value 0 m/s, with substantially uniform deceleration. At the moment of response of for instance a safety element, a brake ramp is activated, whereby a uniform braking with linear deceleration can be achieved, while observing the brake path defined in the corresponding regulations. The regulator contains deceleration values as nominal value(s), which are intermittently compared to preferably speed values of the drive motor of the escalator or moving walkway.
According to further aspects of the invention, the brake magnet can be controlled independently from the power supply of the drive motor. This requires a slightly higher effort, since an independent power supply has to be provided; but for certain applications, in particular regarding technical safety aspects, these use applications are considered as a further alternative for improving the object of the invention in a useful way.